Oxygen liberating compositions



Patented Apr. 3, 1951 OXYGEN LIBERATING COMPOSITIONS Carey B. Jackson, Forest Hills, Pa., assignor to Mine Safety Appliances Company, Pittsburgh, Pa., a corporation of Pennsylvania N Drawing. Application August 24, 1944, Serial No. 551,055

oxygen generating materials because, for example,

they can be used for the rapid generation of large quantities of substantially pure oxygen by the controlled addition of a suitable reagent, for instance in generators of the Kipp type. More particularly, they have been proposed for use in breathing apparatus because these peroxides have the ability to react with moisture and carbon dioxide in exhaled air with fixation of the carbon dioxide and quantitatively equivalent liberation of oxygen. Thus they are adapted for use in breathing apparatusof the self-contained type that is used in non-respirable atmospheres, for high altitude flying, and other purposes where it is necessary to provide oxygen or to breathe the same air in a closed circuit.

One way. of providing oxygen forsuch purposes is to supply it from a source of compressed oxygen,

commonly referred to as bottled oxygen. This is undesirable in self-contained breathing apparatus because of the weight of the oxygen bottle with the necessary pressure regulating mechanism. Or, if the oxygen is supplied from a bottle to a simple respirator from which exhaled air is discharged to the atmosphere with each exhalation, the preponderance of the oxygen supplied is wasted. For these reasons the use of alkali metal peroxides as oxygen liberating materials as used in breathing apparatus has become more important.

Until recently sodium peroxide or mixtures of sodium peroxide and potassium tetroxide have been used for such purposes, the mixtures being preferred because they provide more available oxygen per unit of weight than does sodium peroxide. It would be desirable to increase the available oxygen still further because thereby a canister would afford longer useful life Pure potassium tetroxide is a material that would accomplish that purpose because ideally it will supply 236 cc. of oxygen per gram of the tetroxide whereas the mixed sodium-potassium peroxide that has been used extensively only supplies from about 190 to 200 cc. per gram of the mixture. If pure potassium tetroxide could be used, therefore, a canister containing it would have an appreciably longer useful life than a similar canister containing the mixed peroxides.

Experience has shown that certain difiiculties attend attempts to use pure potassium tetroxide for these purposes. Thus, pure anhydrous potas- 2 Claims. (ores-184) of peroxide.

sium tetroxide does not react promptly with exhaled air when the canister containing'the peroxide is at subnormal temperatures, e. g., 0 F. It is a prime requisite of breathing apparatus of this type that the oxygen-liberating material shall react immediately and substantially quantitatively under such conditions. On the other hand, the canisters containingthese materials are sealed to prevent deterioration in storage, so that when put in use they will be fully efiicient. If it is attempted to apply to pure potassium tetroxide the practice that has been found to be satisfactory with the sodium and potassium peroxide mixture that has been used up to the present time, it is found that excessive pressure may develop within the canisters, particularly when they are stored at super-atmospheric temperatures, e. g., up'to temperatures of the order of F. The pressure may, and commonly will, cause the canister seal to burst. Such conditions may be encountered, for example, with canisters in storage in the Tropics, which may easily reach such temperatures.

It is among the objects of this invention to provide pure potassium tetroxide which is fully adapted for use in breathing apparatus, is stable in sealed containers at temperatures of the order of 150? F., and reacts promptly and quantitatively with exhaled air at temperatures as low as 0 F.

The invention is predicated upon my discovery that exceedingly small amounts of water suflice to condition pure potassium tetroxide for prompt and quantitative reaction with exhaled air at low temperatures, and further that stability at supernormal temperaturesis insured by restricting the amount of water within extremely narrow and critical limits.

The limits upon the amount of water tolerable in the practice of the invention are not only critical but are of an entirely diiierent order of magnitude from those used in prior practice with the commercially applied sodium and potassium peroxide mixture, and apparently the Water which is used in the practice of the inventionserves a difierent function from that used in preparing the mixed peroxides.

More particularly, I have found that prompt reactivity at low temperatures and stability at abnormally high atmospheric temperatures are to be had by providing pure potassium tetroxide with at least about 0.02 but not more than about 0.06 mol of water per mol of the peroxide, which corresponds to about 0.4 to 1.1 gm of water per mol This is to be contrasted with the prior art proposals and practice, according to which sodium peroxide or the mixed peroxides were provided with from about 0.25 mol of water per mol of peroxide, and even with as much as one mol per mol.

Under the prior art proposals the water added acted, at least chiefly, to effect adequate bonding of the peroxide. The amounts of water tolerable in accordance with the present invention are so small, however, as evidently to have little or no bonding efiect, and as indicated above, the.

amounts of water that have been used heretofore cause the pure potassium peroxide to be unstable.

The critical nature of the limits stated is evidenced by the 'fact that, as experience has shown, pure potassium tetroxide containing less than 0.02 mol of water per mol of peroxide will not react, or will not react adequately, with exhaled air at F., and that if more than about 0.06 mol of water per mol of the pure peroxide is present pressure within sealed containers of the material may, and. probably will, develop when they are stored at supernormal atmospheric temperatures.

Pure potassium peroxide as made is essentially anhydrous. The deliberate addition of the small amounts of water stated would interpose an operating and control difficulty, at least in large scale operation. I have discovered, however, that the peroxide can be provided easily with the proper amount of water by exposing it to the atmosphere in relatively thin layers for absorption of moisture from the air. At periodic intervals a sample is taken and an accurately weighed portion of it is heated gently with collection and measurement of the gas evolved. Tested in this,

way the tetroxide should evolve at least 5 cc. but not over about 15 cc. of oxygen per gm. These values correspond to those stated above.

According to the provisions of the patent statutes, I have explained the principle of my invention and have described what I now consider to represent its best embodiment. However, I

desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. A sealed canister, constructed for use in a self-generating oxygen breathing apparatus, containing substantially pure potassium tetroxide carrying from about 0.02 to 0.06 mol of water per mol of tetroxidc, said water conditioning the tetroxide to be stable at temperatures up to about F. and to react rapidly with carbon dioxide, upon opening of the canister seal, to liberate oxygen at temperatures of about zero degreesF.

2. A sealed moisture impervious container containing' substantially pure potassium tetroxide carrying from about 0.02 to 0.06 mol of water per mol of tetroxide and conditioned by said water to be stable insaid container at temperatures up to about 150 F. and also to react rapidly at a temperature of about 0 F. upon contact with carbon dioxide and moisture to lib- ,erateoxygen, and said container preventing deterioration of said properties during storage therein.

CAREY B. JACKSON.

REFERENCES CITED The. following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Gerson June 14, 1938 OTHER ,REFERENCES Number 

1. A SEALED CANISTER, CONSTRUCTED FOR USE IN A SELF-GENERATING OXYGEN BREATHING APPARATUS, CONTAINING SUBSTANTIALLY PURE POTASSIUM TETROXIDE CARRYING FROM ABOUT 0.02 TO 0.06 MOL OF WATER PER MOL OF TETROXIDE, SAID WATER CONDITIONING THE TETROXIDE TO BE STABLE AT TEMPARATURES UP TO ABOUT 150* F. AND TO REACT RAPIDLY WITH CARBON DIOXIDE, UPON OPENING OF THE CANISTER SEAL, TO LIBERATE OXYGEN AT TEMPERATURE OF ABOUT ZERO DEGREES F. 